Living materials with programmable functionalities grown from engineered microbial co-cultures

Abstract

Biological systems assemble tissues and structures with advanced properties in ways that cannot be achieved by man-made materials. Living materials self-assemble under mild conditions, are autonomously patterned, can self-repair and sense and respond to their environment. Inspired by this, the field of engineered living materials (ELMs) aims to use genetically-engineered organisms to generate novel materials. Bacterial cellulose (BC) is a biological material with impressive physical properties and low cost of production that is an attractive substrate for ELMs. Inspired by how plants build materials from tissues with specialist cells we here developed a system for making novel BCbased ELMs by addition of engineered yeast programmed to add functional traits to a cellulose matrix. This is achieved via a synthetic 'symbiotic culture of bacteria and yeast' (Syn-SCOBY) approach that uses a stable co-culture of Saccharomyces cerevisiae with BC-producing Komagataeibacter rhaeticus bacetria. Our Syn-SCOBY approach allows inoculation of engineered cells into simple growth media, and under mild conditions materials self-assemble with genetically-programmable functional properties in days. We show that co-cultured yeast can be engineered to secrete enzymes into BC, generating autonomously grown catalytic materials and enabling DNA-encoded modification of BC bulk material properties. We further developed a method for incorporating S. cerevisiae within the growing cellulose matrix, creating living materials that can sense chemical and optical inputs. This enabled growth of living sensor materials that can detect and respond to environmental pollutants, as well as living films that grow images based on projected patterns. This novel and robust Syn-SCOBY system empowers the sustainable production of BC-based ELMs.

Engineering Bacterial Cellulose by Synthetic Biology

“…The many possibilities of using synthetic biology to program protein secretion into growing bacterial cellulose were highlighted recently in work that took an alternative 'co-culture' approach to making BC-based materials with new functional properties. Taking inspiration from the symbiotic culture of bacteria and yeast (SCOBY) that is used traditionally to ferment kombucha tea [61], the authors devised a symbiotic culture of K. rhaeticus and S. cerevisiae yeast that grows efficiently on sucrose and produces thick BC pellicles that contain within them both the bacteria and the yeast cells [62]. The synthetic biology was in this case not applied to BC-producing bacteria but instead to the co-cultured yeast.…”

“…In response to this sensing the cells were engineered to secrete enzymes or to produce fluorescent and luminescent proteins that can be visibly detected from the grown material. The overall result is a way to grow bacterial cellulose and use synthetic biology to program a variety of multifunctional properties to be present into the produced material; from BC materials that break down pollutants, to BC-based 'photographs' that glow in response to light stencils ( Figure 2) [62].…”

Hybrid Living Capsules Autonomously Produced by Engineered Bacteria

“…Recently, Gilbert et al developed a co-culture system in which the model eukaryote Saccharomyces cerevisiae is stably maintained among BC-producing bacteria during cellulose production. The yeast provides an engineerable host cell within the growing material that can be rationally programmed at the genetic level for dedicated tasks (38).…”

Bacterial cellulose spheroids as building blocks for 2D and 3D engineered living materials

“…In the last decade, progress in understanding and producing BC has now led to its use in a broad range of applications, including products used in textiles, cosmetics, healthcare, audio-visual technology and architecture 8–11 . Most of these applications use sterile, purified BC as a bulk specialised material, however bacterial cellulose has also shown promise as an ELM 12,13 . In one recent example, incorporating Bacillus subtilis cells into BC-based wound dressings helped to prevent wound infections by blocking the growth of several pathogenic bacteria 14 .…”